The overall goal of the experiments comprising this project are twofold; to provide material and assays for drug screening, and to provide as rapidly as possible the protein structure component of a developing anti- AIDS drug design programme, using primarily the 2D NMR-restrained molecular dynamics method. The initial targets are CD4 and gp120, since interference with CD4-gp120 by antibodies to the CD4 protein interaction by using monoclonal antibodies to the CD4 protein has already been shown to prevent HIV replication and a simple binding assay is available that is suitable for large-scale drug screening prospects. Subsequent targets will include the tat protein and others that are defined by the research in projects 1 and 3. In order to interface with the drug screening project, convenient assays for each of these new targets beginning with the tat protein, must be established. The molecular biology part of the project will this consist of a series of experiments aimed at optimising the expression and purification of domains of CD4 and gp120. If time and funding allows, a similar approach can be initiated for tat, other HIV and HIV-relevant cellular proteins or their domains. Biophysics and drug design will begin as soon as sufficient amounts of a domain of CD4 (or another protein) with properties that allow analysis of NMR spectroscopy or X-ray crystallography can be produced. The ability of each protein/domain to form crystals will be investigated collaboratively by Allexlix scientists and Project 2. In this project, Allelix scientists in collaboration with Drs. Clore and Gronenborn of NIH will concentrate on the generation of protein structural information by 2D NMR spectroscopy. The discovery in project 5 of organic chemicals that interfere with CD4-gp120 interaction, combined with knowledge of protein structure from this project, will then allow rapid progress in the design of effective drugs that block this interaction. The same powerful combination of initial screening followed by protein-structure based rational drug design will then be followed for other protein targets or AIDS therapy.